Oyster shells, shards of glass, coal, nails, ceramic pipe stems, a 1918 liberty dime, even a glass Yoo-hoo bottle — each is a clue to the history of Beallsville's Darby Store.

A team of volunteer archaeologists is spending three weeks this summer excavating around the historic site at the corner of Beallsville and Darnestown roads, which has been occupied by various buildings since the nineteenth century. The Maryland-National Capital Park and Planning Commission purchased the store and adjacent Darby House for $670,000 in 2004, a year after the nonprofit Montgomery Preservation Inc. declared the deteriorating building one of the county's most endangered historic sites.

The building will be stabilized by the end of the year, says county cultural resources planner Julie Mueller. If the stabilization goes as planned, the structure will be moved back from the corner sometime next year, she said.

The volunteer archaeologists are excavating key areas around the store and its future site before any artifacts buried in the ground are lost to history forever.

"It's kind of a puzzle you have to put together," Mueller said. The county conducts archaeological digs whenever it needs to disturb the land at a historic site, she said.

Excavations are particularly important when "there are layers of history, like at the Darby Store," Mueller said.

A store and blacksmith shop were built on the corner, now part of the Beallsville Historic District, in the mid-nineteenth century and demolished by Harry C. Darby after he bought the land in 1908, according to county documents. He built the two-and-a-half-story general store in 1910, where residents bought supplies and picked up their mail until it closed in 1974. A tractor-trailer destroyed the front porch in the late 1980s.

The site remained a viable commercial outpost after the Metropolitan Branch of the Baltimore and Ohio Railroad opened in 1873, even though it didn't stop in Beallsville because travelers from Poolesville and Rockville passed through the crossroads on their way to upcounty stations, according to Don Housley, president of the Mid-Potomac Chapter of the Archeological Society of Maryland.

"Usually when the railroad came in, if it didn't go through your town then your town was dead, but Beallsville continued," Housley said.

Darby's son used the building for storage, and it was filled wall-to-wall with everything from wheelbarrows, old sofas and paint cans to historic receipts and ledger books that will help researchers complete the puzzle, Mueller said.

Last week, about 10 volunteers worked their way through layers of clay soil marked into small grids, stopping only when they no longer found artifacts. Items such as nails and pieces of glass were documented, placed into labeled bags and set aside for further analysis.

"Artifacts are important to us only in the context that they're found. A lot of people go to Civil War battlefields and find bullets, but once you remove it, it loses its context," volunteer Mike Robinson, 63, of Rockville said as he sifted through clods of soil. "Archaeology is a destructive science. Once you dig a hole and take an artifact out, it can't be replaced."

For details about county archaeology programs, including camps and volunteer opportunities, visit www.montgomeryparks.org/PPSD/